Genesis of the Yidonglinchang gold deposit, Lesser Xing’an Range, China: Insights from fluid inclusions, H-O-S-Pb isotopes, and Sm-Nd and U-Pb geochronology

Abstract

The origin and evolution of the newly discovered Yidonglinchang gold deposit in the Lesser Xing’an Range, Northeast China, remain poorly understood. This article focuses on the investigations of the geological characteristics, fluid inclusions, H-O-S-Pb stable isotopes and geochronology of the deposit. The Yidonglinchang gold deposit is mainly controlled by NEE-trending faults, and the ore bodies are present in volcanic rocks of the Early Cretaceous Ningyuancun Formation (K1n). Silicification, pyritisation, and argillization zones develop sequentially from near the ore center outwards. The ore minerals mainly include electrum and argentite. The gangue minerals are mainly quartz, calcite, and a small amount of sericite, plagioclase and adularia. The main gold-bearing minerals are quartz and calcite. The primary fluid inclusion types in quartz are pure-liquid-phase, gas-rich-phase, and liquid-rich-phase inclusions. Most of the inclusions are classified as a H2O-NaCl system which were formed under low-temperature, low-salinity conditions, indicating that Yidonglinchang is an epithermal gold deposit. The occurrence of boiling fluid inclusion assemblage indicates that the fluids underwent decompression boiling. Sm-Nd dating of calcite from the main ore-forming stage yields an age of 97.5 ± 2.3 Ma, which is interpreted as the timing of mineralisation. Zircon U-Pb dating of dioritic porphyrite yields ages of 98.8 ± 1.1 and 98.0 ± 1.3 Ma, which are consistent with the mineralisation age, suggesting a potential genetic link between the intrusive rocks and the ore formation. H-O-S-Pb isotopic compositions indicate that the ore-forming fluids were magmatic water during the early mineralisation stage, with the addition of meteoric water during the late stage. These isotopic compositions are also indicative of an origin of the ore-forming materials from the mixed crustal and mantle components. The mineralisation of the Yidonglinchang gold deposit was related to the slab rollback of the subducted Palaeo-Pacific Plate in the early Late Cretaceous.